A wide variety of seat belt retractors have been developed for preventing belt protraction during periods of rapid acceleration or deceleration of a vehicle. Many of these seat belt retractors include a reel, upon which a seat belt is wound, having a ratchet wheel with teeth for being engaged by a pivotally frame-mounted pawl. The pawl is normally biased in a non-engaging position in which the pawl is spaced from the ratchet wheel, and for preventing belt protraction, the pawl is commonly actuated into engagement with the ratchet wheel by an inertial mechanism operating in response to such periods of rapid acceleration or deceleration of the vehicle.
However, during vehicle operation periods of constant speed or modest acceleration or deceleration, the pawl is typically biased, such as by gravity, to its non-engaging position with respect to the ratchet wheel, and hence, the pawl is free to pivot to abut the ratchet wheel in response to any vehicle vibration. Since the pawl and ratchet wheel are typically formed from metal, this abutment produces a rattle which may be disturbing to the driver and passengers and to those who are called upon to identify such rattle.
For many applications, however, it is desirable that seat belt retractors be provided with a noise suppression mechanism to quiet any such noise or rattle occasioned by such free movement of the pawl into the ratchet wheel during normal vehicle operation.
In this connection, much effort has been directed toward developing fail-safe noise suppression mechanisms that do not adversely affect the operation of the retractor's components, such as any emergency locking mechanisms employed for actuating the pawl into the ratchet wheel for preventing belt protraction. It also is important that these noise suppression mechanisms are capable of being cycled to insure their ability to operate under adverse conditions, and of meeting the requisite safety code specifications of the government and of the particular installer of such retractor.
The disadvantage of some noise suppression mechanisms intended to quiet the rattle occasioned by free movement of the pawl is either their tendency to adversely affect the operation of any emergency locking mechanism, such as an inertial mechanism, their inability to effectively cooperate with an emergency locking retractor employing an inertial mechanism and, in many applications, their tendency to render the retractor too large, complex and/or expensive.
The present invention pertains to a fail-safe, cost effective noise suppression mechanism which is sized accordingly so to be completely self-contained within an emergency locking retractor employing an inertial mechanism. The noise suppression mechanism is formed of relatively few and simple parts making it very cost effective.
As known in the art, it is common for noise suppression mechanisms to include some type of blockout means for engaging the pawl to space it from the teeth of the ratchet wheel. One example of such attempts is U.S. Pat. No. 4,220,294 to DiPaola which utilizes a flexible means for spacing the pawl from the ratchet teeth. A disadvantage with employing this flexible means is that it remains in constant contact With the pawl during normal operation and, as a result, tends to lessen the sensitivity of the pawl to the actuator or inertial mechanism. Thus, this type of noise suppression mechanism may render retractors unsafe due to its inability to freely respond to the inertial mechanism.
In response, efforts have been made to space the pawl from the ratchet wheel in seat belt retractors without lessening the sensitivity of the pawl to the inertial mechanism. Such attempts include using a rotational force generated from the protraction of the belt. The rotational force is captured, via a friction spring, to pivot a lever into an operative position to space the pawl out of engagement with the ratchet wheel. Examples of such retractors are shown in U.S. Pat. No. 4,749,142 to Saitow, U.S. Pat. No. 4,993,656 to Tsuge et al. and U.S. Pat. No. 5,002,601 to Saitou et el. A disadvantage with these mechanisms is that the lever is only being actuated when the rotational force is generated during belt retraction. This is generally undesirable because during much of the time when the vehicle is under normal operation the seat belt is not being retracted, and thus, there is no rotational force being generated.
Another known retractor responding to belt protraction is disclosed in U.S. Pat. No. 3,862,726 to Ulrich et al. as including a blockout means being actuated to immobilize a pawl against engagement with the ratchet wheel during belt protraction. This patent discloses a blockout means on a disc which rotates in response to belt protraction and retraction to rotate between an operative position and an inoperative position. A disadvantage with this design is that the blockout means is designed for a retractor in which the pawl is continuously biased into engagement with the ratchet wheel and which includes an inertial mechanism responsive only to rapid accelerated belt protraction and not to rapid acceleration or deceleration of the vehicle.
It is further noted that there have been found in the art other applications of discs being similarly rotatable with the ratchet wheel. However, these discs have been used primarily to actuate automatic locking mechanisms in retractors and do not contemplate the present considerations relating quieting retractors utilizing emergency locking mechanisms in which an importance exists to not adversely affect any such emergency locking mechanism.
There is a need for a noise suppression mechanism which operates to block a pawl which is constantly biased out of engagement with the ratchet wheel in a retractor having an inertial mechanism responsive to rapid acceleration and deceleration of the vehicle.
A general object is to provide an emergency locking retractor employing an inertial mechanism with a fail-safe, small, self-contained noise suppression mechanism for immobilizing the pawl and inertial mechanism during periods except when the belt is being protracted as occurs at the time of an accident.
A further object is to provide a noise suppression mechanism which is highly durable, efficient, and cost effective to manufacture, install and operate.